Variable mode timing with divergence inhibit

Abstract

A method is disclosed herein. The method includes receiving, by a processor, an ejection command for ejecting an ejection seat from an aircraft; determining, by the processor, an equivalent airspeed and an equivalent altitude of the ejection seat; and, responsive to the airspeed and the altitude indicating a second mode of operation: sending, by the processor, a command to deploy a drogue parachute; determining, by the processor, a variable drogue severance delay; and responsive to the variable drogue severance delay expiring, sending, by the processor, a command to sever the drogue parachute and deploy a main parachute.

What is claimed is: 
     
       1. A method, comprising:
 receiving, by a processor, an ejection command for ejecting an ejection seat from an aircraft; 
 determining, by the processor, an equivalent airspeed and an equivalent altitude of the ejection seat; and 
 responsive to the airspeed and the altitude indicating a second mode of operation:
 sending, by the processor, a command to deploy a drogue parachute; 
 determining, by the processor, a variable drogue severance delay; and 
 responsive to the variable drogue severance delay expiring, sending, by the processor, a command to sever the drogue parachute and deploy a main parachute. 
 
 
     
     
       2. The method of  claim 1 , wherein the variable drogue severance delay is determined using at least one of a polynomial calculation, a quadratic calculation, or a linear calculation, to include minimum and maximum bounds. 
     
     
       3. The method of  claim 2 , wherein the polynomial calculation uses a static pressure of the ejection seat for the equivalent altitude, a dynamic pressure of the ejection seat for the equivalent airspeed, and four constants. 
     
     
       4. The method of  claim 3 , wherein the static pressure is determined using a static pressure sensor coupled to the ejection seat. 
     
     
       5. The method of  claim 3 , wherein the dynamic pressure is determined using at least one dynamic pressure sensor coupled to a pitot tube coupled to the ejection seat. 
     
     
       6. The method of  claim 1 , further comprising:
 responsive to the airspeed and the altitude indicating a first mode of operation, sending, by the processor, a command to deploy the main parachute without deploying the drogue parachute. 
 
     
     
       7. The method of  claim 1 , further comprising:
 responsive to the altitude indicating a third mode of operation:
 sending, by the processor, the command to deploy the drogue parachute; 
 determining, by the processor, whether a predetermined altitude has been achieved and whether a minimum viable delay has expired; and 
 responsive to the predetermined altitude being achieved and the minimum delay being expired, sending, by the processor, the command to sever the drogue parachute and deploy the main parachute. 
 
 
     
     
       8. The method of  claim 1 , wherein the determining of the airspeed and the altitude of the ejection seat is further based on an equivalent altitude and an equivalent airspeed relative to sea level conditions. 
     
     
       9. A system, comprising:
 an ejection seat including a drogue parachute and a main parachute; 
 a dynamic pressure sensor; 
 a static pressure sensor; 
 a processor; and 
 memory operatively coupled to the processor, the memory comprising instructions stored thereon that, when executed by the processor, cause the processor:
 determine an equivalent airspeed of the ejection seat using the dynamic pressure sensor; 
 determine an equivalent altitude of the ejection seat using the static pressure sensor; and 
 responsive to the airspeed and the altitude indicating a second mode of operation:
 send a command to deploy the drogue parachute; 
 determine a variable drogue severance delay; and 
 responsive to the variable drogue severance delay expiring, send a command to sever the drogue parachute and deploy the main parachute. 
 
 
 
     
     
       10. The system of  claim 9 , wherein the variable drogue severance delay is determined using at least one of a polynomial calculation, a quadratic calculation, or a linear calculation, to include minimum and maximum bounds. 
     
     
       11. The system of  claim 10 , wherein the polynomial calculation uses a static pressure of the ejection seat for the equivalent altitude, a dynamic pressure of the ejection seat for the equivalent airspeed, and four constants. 
     
     
       12. The system of  claim 11 , wherein the static pressure is determined using the static pressure sensor coupled to the ejection seat. 
     
     
       13. The system of  claim 11 , wherein the dynamic pressure is determined using at least one dynamic pressure sensor coupled to a pitot tube coupled to the ejection seat. 
     
     
       14. The system of  claim 9 , wherein the instructions further cause the processor to:
 responsive to the airspeed and the altitude indicating a first mode of operation, send a command to deploy the main parachute without deploying the drogue parachute. 
 
     
     
       15. The system of  claim 9 , wherein the instructions further cause the processor to:
 responsive to the altitude indicating a third mode of operation:
 send the command to deploy the drogue parachute; 
 determine whether a predetermined altitude has been achieved and whether a minimum viable delay has expired; and 
 responsive to the predetermined altitude being achieved and the minimum delay being expired, send the command to sever the drogue parachute and deploy the main parachute. 
 
 
     
     
       16. An ejection seat, comprising:
 a drogue parachute; 
 a main parachute; 
 a dynamic pressure sensor; 
 a static pressure sensor; and 
 an electronic sequencer configured to:
 determine an equivalent airspeed of the ejection seat using the dynamic pressure sensor; 
 determine an equivalent altitude of the ejection seat using the static pressure sensor; and 
 responsive to the airspeed and the altitude indicating a second mode of operation:
 send a command to deploy the drogue parachute; 
 determine a variable drogue severance delay; and 
 responsive to the variable drogue severance delay expiring, send a command to sever the drogue parachute and deploy the main parachute. 
 
 
 
     
     
       17. The ejection seat of  claim 16 , wherein the variable drogue severance delay is determined using at least one of a polynomial calculation, a quadratic calculation, or a linear calculation, to include minimum and maximum bounds. 
     
     
       18. The ejection seat of  claim 17 , wherein the polynomial calculation uses a static pressure of the ejection seat for the equivalent altitude, a dynamic pressure of the ejection seat for the equivalent airspeed, and four constants. 
     
     
       19. The ejection seat of  claim 18 , wherein the static pressure is determined using the static pressure sensor coupled to the ejection seat. 
     
     
       20. The ejection seat of  claim 19 , wherein the dynamic pressure is determined using at least one dynamic pressure sensor coupled to a pitot tube coupled to a headrest of the ejection seat.